1. Field of the Invention
One or more embodiments of the present invention relate to a magnetic detection element for detecting a magnetic field intensity and a signal transmission device for transmitting a signal by means of a magnetic coupling.
2. Description of the Related Art
Patent literature 1, for instance, discloses a magnetic coupling type of signal transmission device comprising a coil which generates a magnetic field in accordance with a input signal and a bridge circuit which includes a magnetoresistance effect element (magnetic detection element) to detect the intensity of the magnetic field generated by the coil.
Patent literature 2, for instance, discloses a granular in gap (GIG) configuration in which a pair of yoke films consisting of a soft magnetic material is arranged to guide a large amount of magnetic flux into both side of the granular film exhibiting a giant magnetoresistance effect (generically electric resistance of a material varies by amount more than few % with an external magnetic field), in order to enhance a variation sensitivity of the electric resistance of the granular film exhibiting a giant magnetoresistance effect.
In such GIG configuration, when external magnetic field is inputted, first the yoke consisting of a soft magnetic material having a large magnetic flux density is magnetized, the magnetic flux generated by the large magnetization passes through the granular film exhibiting a giant magnetoresistance effect to achieve large amount of variation in the electric resistance with a small variation of the external magnetic field. However, in the GIG configuration, a linear range where magnetic field intensity can be linearly detected is limited in a significantly narrow range, because of a nonlinear magnetic flux increasing characteristic according to a magnetizing procedure of the soft magnetic material yoke film and to a nonlinear resistance variation characteristic in the magnetoresistance effect of the granular film.
Patent literature 3, for instance, discloses a technique for detecting a very small variation of magnetic flux by providing a magnetic path with a bypass to reduce magnetic flux applied to the detecting coil. In this technique, the magnetic flux variation detection range is widened by reducing the sensitivity, but the range having high linearity in electric resistance can not be widened, and therefore the linearity of the magnetoresistance effect element can not be improved.